Upop stands for unreserved open category ,i.e. , seats under unreserved or general category. ewop stands for economically weaker open category or seats under the 'economically weaker section' category. if you belong to the unreserved category then select urop ad if economically weak category then select ewop .Feel free to ask me in the comment box if you are having any further doubts

hope you find it helpful 

Good Luck